Three invasive Heracleum in Europe
The genus Heracleum (Apiaceae) includes 60–70 species of perennial or biennial herbs, distributed in the temperate northern hemisphere and in high mountains as far south as Ethiopia. Centres of the highest species diversity are the Caucasus Mountains (26 species) and China (29 species), particularly Hengduan Mountains. There are three main invasive Heracleum in Europe: H. mantegazzianum (EPPO List of Invasive Alien plants), H. sosnowskyi (EPPO List of Invasive Alien plants) and H. persicum. They invade disturbed and also undisturbed ecosystems and cause health hazards by burning people’s skin when in contact with them.
Heracleum mantegazzianum is a monocarpic perennial native to the Western Greater Caucasus (Russia, Georgia), where it grows in species-rich, tall-herb mountain meadows, clearings, and in forest margins up to the treeline of 2000 m above sea level. It was introduced as a garden ornamental plant around 1817 and the first naturalized population was documented in Cambridgeshire (GB) in 1828. At present, the species is recorded in at least 19 European countries, and was first noted before 1900 in 14 of these. It is also naturalized in Canada and the United States.
Heracleum sosnowskyi is a monocarpic perennial native to eastern and central Caucasus, Transcaucasia, and northeast Turkey. It was first introduced to Russia in 1947 as a highly productive fodder crop for livestock. Later it was introduced to other countries such as Belarus, Ukraine, the Baltic countries, and former East Germany. The planting schemes have been largely abandoned, although they still continue in parts of Russia.
Heracleum persicum is a polycarpic perennial native to Turkey, Iran, and Iraq. The status of this invasive species in Europe is still not fully resolved. The history of introduction of H. persicum is unclear. It was the first Heracleum species to be described, as early as 1829, and it is likely that some other large Heracleum spp. were misidentified as H. persicum. This makes the tracing-back of the H. persicum invasion into Europe difficult. Compared to the other two species, the distribution of H. persicum in Europe is restricted to Scandinavia. The genetic diversity of these Heracleum species has been investigated using a biogeographical approach. Plants of H. mantegazzianum, H. sosnowskyi, and H. persicum were sampled from across a wide geographical range in both native (Caucasus and south-west Asia) and invaded (Europe) distribution ranges.
The results confirmed that there are three distinct tall Heracleum species invading Europe. Within each of the three species, plants collected in the invaded range are genetically close to those from their native ranges. A close genetic relationship between the three invasive Heracleum species in Europe was also found. A high overall genetic variability detected in the invaded range suggests that rapid evolution, drift, or hybridization played a role in genetic structuring of invading populations. For H. mantegazzianum, genetic distance of populations in the native range significantly decreased with geographical distance, but not in the invaded range. In addition, results indicated that H. laciniatum is probably synonymous with H. persicum.
It is likely that the current pattern of genetic diversity in Europe resulted from multiple introductions of all three species.
Sources
Jahodová Štrybush S, Pyšek P, Wade M and Karp A (2007) Invasive species of Heracleum in Europe: an insight into genetic relationship and invasion history. Diversity and Distributions 13, 99-114. http://www.blackwell-synergy.com/doi/pdf/10.1111/j.1366-9516.2006.00305.x